Pin tap



Nov. 25, 1941.

O. A. BROWN PIN TAP Filed July 8, 1940 Patented Nov. 25, 1941 PIN TAIOra A. Brown, Montebello, Calif., assigner .to Baash-Ross Tool Company,Los Angeles, Calif., a corporation 0f California Application July 8,1940, Serial No. 344,351

17 Claims. (C

This invention relates to well tools and relates more particularly toshing tools useful in recovering objects from wells. A general object ofthis invention is to provide an effective and :dependable pin tap thatmay be readily released in the event the lost object or lish cannot bewithdrawn from the well.

In deep well drilling `operations a `string of pipe sometimes becomes.caught in the well. Where attempts .to withdraw the entire pipe stringas a unit have failed `it is the usual practice to unthread a portion ofthe -string from the upper end of .the well `so .that the portion thusfreed may be recovered. This leaves `a portion of the string in the wellwhich must be recovered by fishing operations. Frequently the remainingportion of the pipe string iits the well so closely that it isimpossible or at least inadvisable to employ an overshot Lor .similarfishing tool. ploy what is known as a pin tap, which -is ya fishing tooldesigned to thread into the upper -end of the fish.

Another object of :this invention is to provide a pin tap operable toyobtain a firm, dependable engagement with the fish for the purpose ofeither unthreading the fish or withdrawing Vthe fish asa unit.

Another object .of this invention is to provide a pin tap having tapslips that may be readily threaded into the iish and then expanded toobtain a strong, positive, engagement with the fish for the purpose ofwithdrawing the fish or u-nthreading a portion of the fish, which slips,may be contracted and unthreaded without endangering or loosening thethreaded connections of vthe iishing string in the event the Ifish`cannot be recovered'or backed oi.

Another object of this invention is to provide a novel and particularlyeffective inclined plane means `for controlling the slips 4and forholding the slips in the expanded 'condition in iirm engagement with the'ish.

Another object of ,this invention is to provide a pin tap embodyingslips .expansible by wedge parts inclined with respect ;to thelongitudinal axis of the tool and screw thread means having threadsoperable 'to produce a rapid initial Vexpansion of the slips and ofsu'ilicient helical pitch to be nonlocking when torque is applied andthreads of smaller helical ang-le operable to produce the final orcontinued expansion of the slips with substantial mechanical advantageto assure a very .tight engagement `of the slips in In such cases itbecomes necessary to Yemi the ish to resist unthreading anddisengagement by vertical forces and rotation.

Another object of this invention is to provide a releasable pin tap ofthe character mentioned in which the tap slips may be expanded,contracted, and fully controlled without endangering the fishing stringor unthreading the threaded .connections of the fishing string.

A further object of this invention is to provide a releasable pin tapthat is compact and sturdy in construction and that embodies means forconducting fluid under pressure to the sh so that circulation may beestablished to iacilitate recovery of the Iish.

The various objects and features of my invention will be fully.understood from the following detailed description of .a typicalpreferred form and application of the invention, throughout whichdescription reference is made to the accompanying drawing, in which:

Eig. A1 is ,a fragmentary vertical sectional View of a portion of a wellshowing the pin vtap of the .present invention rabout to enter the fishin the well. Fig. 2 is an enlarged central longitudinal detailedsectional View of the pin tap showing the slips threaded .in the fishand the upper mandrel `in a partially raised position. Fig. 3 is avfragmentary vertical detailed sectional view with the mandrel ,and nutin side elevation showing the clutch means engaged for the transmissionvvof right hand rotation and Figs. 4 and 5 are transverse detailedsectional views taken 4as -indicated by lines 4 4 and 5-5, respectively,on Fig. .2.

The improved pin .tap of lthe presen-t yinvention may be said Atocomprise, generally, a body In, tap slips l l 4carried bythe body I0andadapted to 'be engaged in a fish F, means I2 for `operating orexpanding the slips `Il and `a control |13 `for facilitating the releaseof the slips.

The body l0 is in the nature of a shell or housing, being an elongate,tubular assembly. In the construction illustrated the body I0 includes.a main tubular section I4 and a guide -sleeve vor nut l5 -threaded in.the upper end of the section i4. The lower end portion I6 of ythe bodysection |.4 is reduced in diameter to present ,an upwardly facing.internal shoulder Il. A ring o r collar VI8 is threaded on the reducedportion i6. The collar I8 has an internalannular shoulder I9 facingupwardly to oppose the .lower end of the portion I6.

The slips Il are arranged at the lower end of `the 'body HJ to engage inthe sh F. In Ythe ,typical use or application of the invention.illustrated the sh F is a portion of a pipe string made up of sectionsS connected by threaded couplings C. The threads of the couplings C willbe considered as righthand threads. As is usually the case the upper endof the lost pipe string or sh F has a tool joint section or couplingsection A provided with an open upwardly facing screW-threaded socket20. The slips II of the pin tap are wedge-like segments designed toengage and thread in the sh socket 20. The slips II are elongate membersarranged in an annular or tubular series of three or more. As bestillustrated in Fig. 5 of the drawing the slips II are arcuate inhorizontal cross section having concave inner sides and convex outersides. The outer sides of the slips II have thread portions 2I whichregister to form a righthand thread for mating with the thread on thewall of the socket 2U. It is preferred to form and relate the slips I Iso thatM the thread made up of the thread portions 2| has a slightlysmaller diameter than the thread on the wall of the socket 26 wherebyslips II readily start and thread in the socket. The slips II areprovided with ShanksV 2'2 which extend upwardly into the collar I8.Downwardly facing shoulders 23 on the slip shanks 22 rest on theshoulder I9. The upper ends of the Shanks 22 engage against or opposethe lower end of the portion I6 so that the slips are constrained tomove vertically with the body I 0.

The means I2 for expanding or operating the slips II is a Wedge meansembodying an inclined plane or thread arrangement and a wedge structure.The means I2 includes a mandrel 24 in the lower portion of the body Iand an upper mandrel 25 extending from the upper end of the body IIJ.The lower mandrel24 shiftably passes through the restricted body portionI6 and extends downwardly into the slip assembly. Sets of verticallyextending wedge parts 2'6 are provided` on the mandrel 24 and cooperatewith complementary wedge parts 2'I on the inner sides of the slips II.The active faces of the wedge parts 26 and 21 are inclined or pitchedrelative to the longitudinal axis of the tool so that the slips areexpanded by relative longitudinal movement between the body I0 and themandrel I2. In the drawing I have shown the slips II fully contracted.

The mandrel 24 and the slips II are keyed or splined to the body III` sothat rotation or torque may be better transmitted from the body to theslips. Spaced longitudinal splines 28 are provided on the mandrel 24 andslidably fit groovesV 29 in the internal wall of the restricted bodyportion I6. The splines 28 may continue downwardly to the lower end ofthe mandrel 2'4 and are slidably received between the vertical edges ofthe slips II to key the slips to the mandrel. An annular enlargement orange 30 is formed on the mandrel 24 and is spaced between the ends ofthe mandrel. The lower face of the flange 30 is engageable with theshoulder I'I to limit the downward travel of the mandrelv relative tothe body I0.

.The upper mandrel 25 of the means I2 slidably passes through the guidesleeve or nut I and its projecting upper end is adapted to be connectedwith a fishing string B. In the case illustrated the upper end of themandrel 25 is threaded .into a sub 3| on the lower end of the fishingstring B. Where the threaded couplings C 'of the s'h F have righthandthreads the couplings D of the iishing string B have lefthand threadsand the threads 32 connecting the mandrel 25 with the sub 3| arelikewise lefthand threads. An annular ange 33 is formed on the mandrel25 to move in the body section I 4 with suitable clearance. The upperside of the flange 33 is formed to cooperate with the lower end of thenut I5 as will be later described. The inner or lower end of the mandrel2'5 is spaced from and opposes the inner end of the mandrel 24.

The spaced opposing mandrels 24 and 25 are Vconnected by an inclinedplane means or screwthread means to produce relative vertical movementbetween the mandrel 24 and the body I0 and to hold the mandrel 24 in aposition where the slips II are expanded. A tube or tubular member 34 isarranged in the body section I4 and receives theopposing end portions ofthe mandrels 24 and 25. The member 34 is received in the body section I4with suitable clearance. Threads 35 connect the mandrel 24 with themember 34 and threads 36 connect the mandrel 25 with the member 34. Thethreads 35 and 36 are pitched in the same direction as the threads ofthe fishing string B and in the case illustrated are pitched in thelefthand direction. The helical pitch of the threads 35 is substantialso that the threads are operable to produce rapid relative movementbetween the mandrel 2'4 and the body` I0 when the slips II are anchoredin the iish F. The threads 35 are preferably square threads and areformed and related to have substantial play or relative verticalmovement so that the mandrel V25 and the sleeve 34 may be `freely movedvertically relative to the body I0 during certain phases of operation.The clearance between the threads 35 is clearly illustrated in Fig. 2.The threads 36 have a smaller helical pitch than the quick threads 35and mate or cooperate with working clearance only. The threads 36 arepreferably square threads and quite heavy. The thread 35 of the mandrel24 extends upwardly from the flange 36 and the thread 36 of the mandrel25 extends downwardly from the flange 33.

It will be seen that with the slips I I engaged in the socket 20,lefthand rotation of the mandrel 25 will cause contraction of themandrels 24 and 25, that is, the mandrels will tend to thread into` themember 34 so that the Wedge parts 26 and 2"I may cooperate to expand theslips II. Righthand rotation of the mandrel 25 with the slips II engagedin the socket 26 will result in expansion or movement of the mandrels 24and 25 with the result that the mandrel 24 will move downwardly so thatthe slips II are free for contraction. The steep or quick threads 35 arenonlocking when a substantial torque is transmitted through the tool forthe unthreading operation. The steep threads 35 also provide for quickinitial slip expansion and contraction while the threads 36 provide forslower but more powerful relative movement to assure the tighterengagement of the slips II in the socket 20 and the sure contraction ofthe slips. With the slips II tightly expanded in the socket 20 thethreads 35 and 36 may lserve to transmit rotation or torque to themandrel 24 and the slips Il.

The control means I3 is a clutch mechanism provided primarily to assurethe release or unthreading of the slips II when it is desired to free totool from the sh F although it may yserve to transmit rotation or torquebetween the man- .drei and the body I0 for other purposes. The controlI3 is :operable 'Lto connect :the mandrel v25 with the body II! :for thetransmission of both righthand and lefthand rotation. ,In ithe typicalconstruction illustrated the Vcontrol I3 :includes cooperating parts ionthe guide sleeve or nut |15 and the mandrel yflange 33. Thelowerendofthe nut I5 is lprovided lwith two Ahelically pitched surfaces38 of slightly lless than .180 each. Vertical or upwardly extendingnotches 39 occur between the ends ofthe helical surfaces 38. Because ofthe helical pitch of the surfaces 38 one wall of 'each notch 39 is of:increased vertical extent to form a substantial longitudinal yshoulder40. The shoulders 49 .face .rearwardly relative to the `righthanddirection of rotation where the threads Y and are lefthand threads, asillustrated. In other words the surfaces -38 are pitched in the samedirection .as the .threads 35 and 36 so that ytheir joinder with thenotches 39 provides for the long .rearwardly facing Ishoulders 40.

The upper side of the flange 33 is provided with a pair of helicalupwardly facing surfaces 4I opposing and complementary to the surfaces38. Upstanding lugs 42 are provided between the ends of the surfaces 4I.The lugs-42 are designed to enter the notches 39. Because of the helicalpitch of the surfaces 4I the forward sides of the lugs 42, relative tothe direction of righthand rotation, are longer than the trailing sidesof the lugs. The forward sides of the lugs 42 are engageable with theshoulders 40 for the transmission of righthand rotation to the body I0before the lugs are engaged in the notches .33 proper. With the lugs 42engaged in the notches 39, by taking up the play in the threads 35, themeans or control I3 is operable to transmit both lefthand and righthandrotation between the mandrel 25 and .the 'body I0. The upper ymandrel.25 is of course movable vertically relative to the body I 0, the extentof this movement being determined or limited .by the engagement of thesub 3| with the upper end of the nut vl5 and the engagement of thesurfaces 4| with the surfaces g` engageable by further relative movementbetween the mandrel 25 `and the Vbody I0 for the transmission of bothrighthand and lefthand rotation.

'I'he invention includes means for l'handling or conducting circulationfluid so that circulation may be established to aid in removing thefish. A 'longitudinal passage 43 is `provided in the upper mandrel 25and its upper end 'communicates with the tubular fishing string B. Asimilar 1ongitudinal fluid `passage 44 is provided in the lower mandrel24. Means is provided for conducting fluid frcm the passage 43 to thepassage 44. This means may comprise a wash pipe 45 threaded or otherwisesecured and sealed in the lower end of the passage 43 and vextendingdownwardly to enter the `passage 44.* A packing gland 46 is provided inthe upper portion of the mandrel 24 to pack about the Iwash ypipe :45.The wash pipe '45 is slida'bly received in the passage 44 and packinggland 46 `and remains in the -pa-ssage `44 .under all operatinglconditions for 'the transmission of fluidto the passage. Means ispreferably provided to discharge the circulation `fiuid into the fish F.A wash ,pipe :4l is secured in the vlower vend of the passage v44 andproject-s .downwardly beyond the mandrel 24 to enter the passage 48 ofthe fish F. Packing r49 may be provided on the wash pipe .41 to sealwith ,the wall of the passage 48.

In operation the tool is run into :the well on .the fishing string Bwith Athe slips Il contracted and the upper and lower mandrels 24 and.25 extended. The -tool `is lowered to the fish F and the slips 4I-I areentered in Vthe fish socket .20. .The string B is turned to the rightwith some weight on the tool to engage the slips II .in the socket 23and to thread the .slips in the socket. Rotation of the string B to theright with asuit- .able Weight on the tool will either result in thetransmission of the `rotation through the mating threads 35 and 35 tothe mandrel 24 or will Acause upward movement .of the mandrel .25 to.engage the lugs 42 with lthe shoulders 40. In either case the.righthand rotation is transmitted `to the `mandrel 24 and the slips IIto thread the slips inthe socket 26. When the slips II have .beenthreaded in the socket 29 a suitable weight may be maintained on thetool and the string B vis turned to the left to .move :the mandrels .2.4and 25 toward one another. This contraction or re1- ative movement ofthe mandrels 24 .and 25 is caused by the cooperation of the threads 3.5and '3.6. As the mandrel 24 moves upwardly during this action the wedgeparts 26 cooperate with the wedge ,parts 21 .to expand the slips II.Instead ofexpanding the slips I I in this manner `a suitable tension .or11p-,pull may be put on the fishing string B to raise the mandrel 24.This mode of operation may be preferable when the slips Il have beeneffectively threaded in the socket 2i! and when the lugs 42 are fullydisengaged from the surfaces 38 and the shoulders 4U. With the slips `II'threaded in the socket 20 and expanded in either of the two ways justdescribed the slips have a firm immovable engagement -with the fish Fand the vlower end of the collar I8 engages the upper end of the fishcoupling member A.

Suitable steps are then taken to withdraw the fish F. The string B maybe raised or pulled upwardly 'in an rattempt to withdraw the entire fishF as a unit. In this case the up-pull is transmitted `through themandrel *25, the member 34 and the mandrel 24 to the slips II which aretightly engaged in the socket 20. Suitable fluid may be pumped throughthe fishing string B to discharge into the fish passage 48 to establishcirculation through the fish. In the event the fish F-'cannot bewithdrawn as a unit by pulling on the string B the string B may bejarred'in an attempt to free or loosen the fish. In raccordance with theusual practice the string B may be provided with a jarring tool orbumper sub (not shown) for the jarring operation. If the Vfish F isloosened or raised either by a simple up-pull on the string -B or lbyjarring operations, the fish is withdrawn from the well.

In the event the fish Fis 'not freed and recovered bythe operationsabove described the string B maybe turned to the left to back off thefish F. 'Lefthand rotation is transmitted from the mandrel 25 to themandrel 24 through the threads '36 and 35 and the ikeys 28 transmit thetorque to the slips I.I. The lefthand torque threads the mandrel25 :downin `'the sleeve Imember 34 and the end of the sub 3l comes against theupper end of the nut I5 and as the lefthand rotation is continued thethreads 35 cooperate to pull the mandrel 24 upwardly relative to thebody I0 so that the slips Il are further expanded and tightened in thesocket 20. The slips II threaded and expanded in the socket 20 transmitthe rotation to the fish F and in most cases the lefthand torque causesunthreading of one of the couplings C of the iish. With one of thecouplings C unthreaded the portion of the fish thus freed may bewithdrawn from the well with the fishing string B. In practice asubstantial lefthand torque may be transmitted through the string B andthe pin tap to the iish to bring about the disconnection of a coupling Cof the iish.

In the event the fish F' cannot be recovered or backed off by the abovedescribed operations it becomes desirable to disconnect the pin tap fromthe fish to permit recovery of the tool and fishing string. Todisconnect or release the pin tap from the iish F the string B is turnedto the right with a slight up-pull applied to the string. This righthandtorque or rotation causes the threads 35 and 35 to move the mandrel 24downwardly and the mandrel 25 upwardly. Downward movement of the mandrel24 relative to the body I0 moves the wedge parts 36 down relative to thewedge parts 37 and the slips l I are free to contract. In thisconnection it will be observed that the non-locking steeply pitchedthreads 35 may produce a quick and substantial downward movement of themandrel 24 for the release of the slips II. Upward movement of themandrel 25 resulting from the righthand rotation of the string B bringsthe lugs 42 against the shoulders 38 and ultimately brings the lugs 42against the shoulders 4I). If the righthand described downward movementof the mandrel 24, the string may be jarred or bumped down to free thewedge parts 26 from the wedge parts 21 for the contraction of the slipsII. With the mandrel 24 moved downwardly to permit contraction of theslip II the string B is raised a short distance to engage the lugs 42 inthe notches 40. In some instances it may be necessary to turn the stringB to the right to move the thread 35 of the member 34 relative to thethread 35 on the mandrel 24 to obtain the required clearance or freedomof movement. The clearance in the threads 35 provides sufficient upwardmovement of the mandrel 25 relative to the mandrel 24 to enter the lugs42 in the notches 4U. With the lugs 42 engaged in the notches 4D thestring B is turned to the left to unthread the slips l I from the socket20. The lugs 42 engaged in the notches 40 transmit this lefthandrotation to the body I0 and the keys 28 transmit the lefthand rotationfrom the body I0 to the slips Il so that the slips are unthreaded fromthe socket 2D. When the slips II have 4been unthreaded from the socket20 the fishing string B carrying the pin tap is withdrawn from the well.

It is to be particularly noted that the quick or steep threads 35prevent locking or binding of the tool when a heavy lefthand torque isapplied and provides for the rapid initial expansion of the slips IIwhile the threads 36 provide for the final positive expansion of theslips. The

threads 35 and 36 serve as torque transmitting elements for thetransmission of rotation from the mandrel 25 to the mandrel 24 when thefishing string B is turned to the left or subjected to lefthand torquefor the purpose of backing 01T the fish F. In other words the threads 35and 3G serve to hold the parts in the positions where the slips II arefully expanded when the pin tap is being employed to unthread or backoff the fish F. The clutch means or control I3 assures the transmissionof lefthand rotation to the slips I I when the slips are to beunthreaded from the fish and thus assures the ready release of the pintap from the Iish in the event the fish cannot be recovered or backedoff.

Having described only a typical preferred form and application of myinvention, I do not wish to be limited or restricted to the specificdetails herein set forth, but wish to reserve to myseif any variationsor modifications that may appear to those skilled in the art or fallwithin the scope of the following claims:

Having described my invention, I claim:

l. A well tool for engaging in a threaded opening of an object in a wellcomprising a set of slips for engaging in said opening, a body elementcarrying the slips, a wedge mandrel operable by vertical movementrelative to the body to expand the slips in said opening, inclined planemeans operable by rotation to produce relative vertical movement betweenthe body and mandrel and operable to hold the body and mandrel againstrelative vertical movement with the slips expanded, and means separatefrom the inclined plane means for transmitting rotation from the stringto the slips.

2. A well tool for use on a shing string and adapted to engage in anopening in an object in the well, the tool comprising a set of slips forengaging in said opening, a body element carrying the slips, a wedgemandrel operable by vertical movement relative to the slips to expandthe slips in said opening, screw thread means connecting the mandrelwith the string for operation thereby and operable by torque appliedthrough the string to hold the mandrel in the position where the slipsare expanded, the screw threads of said means having clearance betweentheir threads, and means engageable by taking up said clearance fortransmitting torque from the string to the slips independently of thescrew thread means.

3. A well tool for use on a shing string and adapted to engage in anopening in an object in the well, the tool comprising a body element anda mandrel related for relative longitudinal movement, a set of slipsadapted to enter said opening and carried by the body element forexpansion in said opening upon relative longitudinal movement betweenthe body element and the mandrel, thread parts on the slips forthreading into said opening, and inclined plane means operable byrotation of the string to cause relative longitudinal movement betweenthe body element and the mandrel to expand the slips and operable totransmit torque to the slips through the mandrel.

4. A well tool for use on a shingstring and adapted to engage in anopening in an object in the well, the tool comprising a body element anda mandrel related for relative longitudinal movement, a set of slipsadapted to enter said opening and carried by the body element forexpansion in said opening upon relative longitudinal movement betweenthe body element and the mandrel, thread parts on the slips forthreading into said opening, means for transmitting torque between themandrel. and slips, and cooperatingl inclined plane elementscarried bythe stringV and mandrel operable by turning of the string tocauserelative longitudinal movement between the body element and themandrel forthe expansion. of the slipsand operable by torque on thestring to retain the mandrel in the position where the slips areexpanded so that torque may be transmitted to the object through themandrel and slips.

5. A well tool for use on a shing string and adapted to engage inanopening in an object in thel well, the tool comprising a body elementand' a mandrel related for relative longitudinal movement, a set ofslips adapted to enter said opening and carried by the body element forexpansion in said opening upon relative longitudinal movement betweenthe body element and the mandrel, thread parts on the slipsfiorthreading into said opening, means for transmittingl torque between themandrel andv slips, cooperating inclined plane parts carried by themandrel and string for transmitting rotation in one direction from thestring to the mandrel to thread the slips in said opening and operablefollowing expansion of theslips to transmit torque in the otherdirection for the unthreading of the object, and means for transmittingtorque to the slipsin said other direction independently of the inclinedplane parts to unthread the slips from said opening.

6. A well tool for use on a shing string and adapted to engage in anopening in an object in the well, the toolcomprising a body element anda mandrel related for relative longitudinal movement, a set of slipsadapted to enter said opening and, carried by the body element forexpansion in said opening upcn relative longitudinal movement betweenthe body element and the mandrel, thread parts on the slips forVthreading into said opening, means for transmitting torque between themandrel and slips, cooperating inclined plane parts carried by themandrel and string forv transmitting rotation in one direction from thestring to the mandrel to threadV the slips` in said opening and operablefollowing expansion of the slips to transmit torque in the otherdirection for the unthreading oi the object, and means for transmittingtorque to the slips in said other direction independently of theinclined plane parts to unthread the slips from said, opening, the lastnamed means including engageable clutch parts on the string and bodyelement, and means for transmitting torque between the body and mandrel.

'7. A pin tap useful in recovering a threadedtogether object from a Welland adapted for use on a iishing string, the pin tap comprising atubular body, tap slips on the lower portion of the body adapted tothread into the object and supported for expansion, a Wedge mandrelshiftable relative to the body to expand the slips, an upper mandrelsecured to the string and entering the upper end of the body, a tubularmember receiving the opposing end portions of the mandrels, and pairs ofmating threads on the mandrels and member pitched in the oppositedirection to the threads of said object and operable by rotation of thestring to cause movement of the wedge mandrel to expand and contract theslips.

8. A pin tap useful in recovering a threadedtogether object from a welland adapted for use on a shing string, the pin tap comprising a tubularbody, tap slips on the lower portion of the mandrels and member pitchedin the opposite directionr to the threads of said object and operable byrotation of the string to cause movement of. the. Wedge mandrel to.expand` and contract the slips, one of said pairs of: threads having asteep helical pitchV to cause rapid initial movement of the wedgemandrel.

9. A pin tap useful in recovering a threadedtogether object from a welland adapted for use on a fishing string, the pin tap. comprising atubular body',l tap slips on the lower portion of the body adapted. tothread into the object and` supported for expansion, aV wedge mandrelshiitable relativey to the body to expand the slips, an upper mandrelsecured to the string and entering the upper end of the body, a tubularmember receiving the opposing end portions of the mandrels andpairs ofmating threads on the mandrels and member pitched in the oppositedirection to the threads of said. object and operable by rotationY ofthe string to cause movement of the wedge mandrel to expand and contractthe slips, one of said pairs of threads having a steep helical pitch tocause rapid initial movement of the Wedge mandrel, the other pair orthreads having a smaller helical angle to assure a positive iinalmovement of the wedge mandrel.

l0. A pin tap useful in recovering a threadedtogether object from a welland adapted for use on a iishing string, the pin tap. comprising atubu-` ported for expansion, a Wedge mandrel shiitl able relative to thebody to expand the slips, an upper mandrel secured to the stringI andentering the upper end of the body, means for connecting the body, wedgemandrel and slips against relative turning, inclined parts carried bythe mandrels pitched iny the opposite direction to the threads of theobject, operable by rotation of the stringl to move the wedge mandrel toexpand the slips and thereafter adapted to transmit torque in onedirection for the purpose of unthreading the connections of the object,and clutch parts on the body and upper mandrel engageable for thetransmission of torque in the other direction to unthread the slips fromthe object.

ll. A pin tap useful in recovering a threadedtogether object fromV awell and adapted for use on a fishing string, the pin tap comprising atubular body, tap slips on. the lower portion ci the body adapted tothread into the object and supported for expansion, a wedge mandrelshiltable relative to the body to expand the slips, an upper mandrelsecured to the string and entering the upper end of the body, means forconnecting the body, wedge mandrel and slips against relative turning,inclined parts carried by the mandrels, pitched in the oppositedirection to the threads of the object, operable by rotation of thestring to move the wedge mandrel to expand the slips and thereafterreleasably holding the wedge mandrel in the position where the slips areexpanded, said inclined parts serving to return the wedge mandrel uponrotation of the string in the other direction so that the slips maycontract, and lug and notch means on the body and upper supported forexpansion, a wedge mandrel shiftable relative to the body to expand theslips, an upper mandrel secured to the string and entering the upper endof thebody, means for preventing relative turning between the body,wedge mandrel and slips, a tubularmember receiving the opposing endportions of the mandrels, Working threads connecting the mandrels Withthe member operable upon rotation of the string to shift the wedgemandre1 for the expansion and contraction of the slips and operable totransmit rotation in one direction to thread the slips in the object andto back ofi the connections of the object, and means on the body andupper mandre1 engageable for the transmission of rotation in the otherdirection to unthread the slips from the object.

13. A pin tap useful in recovering a threadedtogether object from a welland adapted for use on a fishing string, the pin tap comprising atubular body, tap slips on the lower portion of the body adapted tothread into the object and supported for expansion, a wedge mandrelshiftable relative to the body to expand the slips, an upper mandrelsecured to the string and entering the upper end of the body, means forpreventing relative turning between the body, wedge mandrel and slips, atubular member receiving the opposing end portions of the mandrels,Working threads connecting the mandrels with the member operable uponrotation of the string to shift the wedge mandrel for the expansion andcontraction of the slips and operable to transmit rotation in onedirection to thread the slips in the object and to back 01T theconnections of the object, means for conducting circulation fluidthrough theV mandrels to the object, and means on the body and uppermandrel engageable for the transmission of rotation in the otherdirection to unthread the slips from the object.

14. A pin tap useful in recovering a threadedtogether object from a welland adapted for use on a fishing string, the pin tap comprising atubular body, tap slips on the lower portion of the body adapted tothread into the object and support-ed for expansion, a wedge mandrelshiftable relative to the body to expand the slips, an upper mandrelsecured to the string and entering the upper end of the body, means forpreventing relative turning between the body, wedge mandrel and slips, atubular member receiving the opposing end portions of the mandrels,working threads connecting the mandrels with the memaccents ber operableupon rotation of the string to shift the wedge mandrel for theexpansionV and contraction of the slips and operable to transmitrotation in one direction to thread the slips in the object and to backoff the connections of the object, the threads allowing verticalmovement of the upper mandrel relative to the body, and clutch parts onthe body and upper mandrel engageable by relative vertical movement forthe transmission of rotation in both directions.

15. A well tool for use on a fishing string and adapted to engage in anopening in an object in the well, the tool comprising a set of slips forengaging in said opening,a body element carrying the slips, a wedgemandrel operable by vertical movement relative to the slips to expandthe slips in said opening, means operable by rotation of the string foractuating and retracting the wedge mandrel, and means for transmittingrotation from the string to the slips independently ofthe last namedmeans.

16. A pin tap useful in recovering a threadedtogether object from a welland adapted for use on a shing string, the pin tap comprising a -tubularbody, tap slips on the lower portion of the body adapted to thread intothe object and supported for expansion, a Wedge mandre1 shiftablerelative to the body to expand the slips, an upper mandrel secured tothe string and entering the upper end of the body, a tubular memberreceiving the opposing end portions of the mandrels, and pairs of matingthreads on the Inandrels and member pitched in the opposite. directionto the threads of said object and operable by rotation of the string tocause movement of the wedge mandrel to expand and contract the slips,one pair of threads being ofV steep helical pitch to prevent locking ofthe threads when the mandrels and member are subjected to heavy,torsional strains.

17. A pin tap useful in recovering a threadedtogether object from a welland adapted for use on a shing string, the pin tap comprising a tubularbody, tap slips on the lower portion of the body adapted to thread intothe object and supported for expansion, a wedge mandrel shiftablerelative to the body to expand the slips, an upper mandrel secured tothe string and entering the upper end of the body, a tubular memberreceiving the opposing end portions of the mandrels. and pairs of matingthreads on the mandrels and member pitched in the opposite direction tothe threads of said object and operable by rotation of the string tocause movement of the vwedge mandre1 to expand and contract the slips,

one pair of threads being of steep helical pitch to prevent locking ofthe threads when the mandrels and member are subjected to heavytorsional strains, the other pair of threads being of lesser helicalpitch to provide great mechanical advantage for the expansion of theslips.

ORA A. BROWN.

